sourceIlo=pi(1)*targetIlo+pi(2)*targetJlo+oi
sourceIhi=pi(1)*targetIhi+pi(2)*targetJhi+oi
INTEGER pi(2), pj(2), oi, oj, tN
pi(1) =exch2_pi(1,N,myTileId)
pi(2) =exch2_pi(2,N,myTileId)
DO pi = 1, nPx
bi0(pi) = pi
INTEGER bi, bj, pi, pj
& pi*exf_half)